A large part of all the freight which is transported in the world is currently transported with the aid of containers. Loading and unloading of containers is often realized with the aid of trucks, cranes, etc. and with specially adapted lifting devices, so-called container yokes. It is important that these container yokes can be quickly adjusted to different container sizes, so that the handling of the containers is time-effective. This adjustment is normally realized with the aid of hydraulic or chain-driven systems.
A drawback with hydraulic systems is that they sooner or later begin to leak hydraulic oil, which contaminates both containers and terminals. This leads to the terminal companies in many countries being forced to pay substantial fines for oil running down in the runoff water. Hydraulic systems are also based on the continuous running of hydraulic pumps, which means higher energy consumption and that the noise level is disturbing in the terminal and for its surroundings.
Chain-driven systems have the drawback that they regularly have to be lubricated and adjusted/tensioned and that they also generate a great deal of mechanical hubbub. Moreover, a chain is less flexible and less stretchable and totally rigid in the lateral direction, which means that the truing of the chain system in the lateral direction is very sensitive and calls for narrow tolerances. This is a problem in an environment in which the container yokes are subjected to large, and, not infrequently, sudden mechanical stresses in the form of shocks and bangs.
Container yokes according to the prior art are relatively expensive to produce and to use and adversely affect the environment and, moreover, are relatively sensitive to mechanical stresses. For these reasons, it is desirable to, as far as possible, diverge from this prior art and replace it with better solutions which are quieter, cleaner, cheaper, more energy efficient and more resistant to mechanical stresses. The prior art within the field does not satisfactorily solve these problems.